1. Field of Invention
The present invention relates to a control system for heating or cooling equipment. More particularly, the invention concerns an intelligent system for efficiently heating or cooling an item of equipment such as a gasoline combustion engine, by selectively applying power to one or more heating or cooling devices, in response to certain input parameters.
2. Description of Related Art
Most gasoline combustion engines become more and more difficult to start with lower and lower ambient temperatures. This presents a formidable problem in cold climates, where automobile engines can be especially difficult to start during the winter season. Even if a cold engine can be started, starting the engine at a less-than-optimum temperature significantly increases the wear and stress experienced by the engine.
A common solution to this problem is to pre-heat the engine before starting it. Engines have been pre-heated with a variety of known heaters. Such heaters are typically used to heat the engine's circulating coolant or the engine's lubricant. These heaters usually require some modification to the engine. For example, some circulating coolant heaters require a heating element to be connected in the circulating water system, and others require a freeze plug to be attached to the engine block. With another type of heater, a device is placed into the dip stick column of the lubricant well. A more primitive approach is to simply place a heat generating device such as a flood lamp or a space heater under the engine to directly heat the engine by convection.
Although some of the above-mentioned heaters burn liquid or gaseous fuel, many utilize an electric heating element that operates on alternating current (a.c.) power from a source such as a wall outlet. In many cases, the vehicle's user leaves the heater running continuously throughout the night. Alternatively, the user may manually connect the heater to electrical power a sufficient time before starting the engine; another option is for the owner to use a timer switch to connect the heater to electrical power at a selected time.
A number of automobile engine heaters are discussed in various patents, such as U.S. Pat. No. 5,048,753 ('753), entitled "Portable Engine Preheating System," issued on Sep. 17, 1991 to Michael Kellie. The '753 patent concerns a portable engine preheating system with a timer-operated heating cycle, where a thermostat overload protection system operates if the temperature of the engine rises above a predetermined critical value.
Another example of an automobile engine heating system is U.S. Pat. No. 3,877,639 ('639), entitled "Auxiliary Automobile Heater," issued on Apr. 15, 1975 to Charles Wilson and George Wilson. The '639 patent involves an automobile heating system in which a gasoline-fueled heater operates for a heating cycle of adjustably predetermined duration. The duration of the heating cycle is selectively determined either by a timer or by remote radio control. The heating cycle may be automatically activated when the ambient temperature drops below a predetermined value. If this occurs, the heating cycle will then terminate once the engine temperature reaches a second predetermined value. The '639 patent utilizes a battery heater in addition to the engine heater.
Since electricity rates for many consumers today are higher than ever, many people reduce their electricity consumption to save money. Additionally, many people conserve electricity for environmental reasons, since they realize that most electrical power plants generate electricity by burning fossil fuels. In this context, the previously-mentioned heating systems are not as advantageous as some might like, although such devices may be useful for certain applications. In particular, these devices are limited, since their engine heating cycles may be longer than the minimum time necessary. Arrangements that use timers are optimally efficient only if the user knows in advance how much heat will be required to safely start the vehicle's engine; this quantity depends upon the engine's size, the ambient temperature, the heater's power rating, and other related factors. For most drivers, such calculations are inconvenient or even impossible. Even if the user is capable of making such calculations, mistakes may lead to an inadequate preheating cycle, and an engine that will not start. Therefore, the previously-discussed methods are limited, and, as a result, they waste electrical power or they are unreliable.
Furthermore, these types of devices are not as beneficial as some might require, since they do not enable simultaneous operation of diverse types of heaters such as auxiliary engine heaters, vehicle interior heaters, battery heaters, and transmission heaters. Additionally, these systems do not accommodate a user who decides not to start his/her vehicle, since these systems permit the engine heaters to run indefinitely.